90 BRITISH DESMIDIACEJE. 



oblong-elliptic, ratio of axes about 1 : 2*4. Cell-Avail 

 smooth. Chloroplasts axile, one in each semicell, with 

 a central pyrenoid. 



Z y go sp or e unknow n . 



Length 14-22 p. ; breadth 15-22 p; breadth of isth- 

 mus 4-7 /JL; thickness 6*511 ft. 



ENGLAXD.- -Angle Tarn, Cumberland ! Pilmoor, N. 

 Yorks ! Epping Forest, Essex ! Twenty-foot River 

 between March and Gruyhirne, Cambridge ! Harefield, 

 Middlesex ! Bisley Common, Surrey ! Slapton Sands, 

 Devonshire ! Xear The Lizard, Cornwall ! 



SCOTLAND. Orkneys ! Shetlands ! 



/ 



IRELAND. Duno*loe and Louerh Connell, Donegal ! 



o o O 



Near Recess, Galway ! 



Geogr. Distribution. --Germany. Galicia in Austria. 

 Norway (form). Sweden. Finland. N. Russia. 

 Faeroes. Greenland. Siberia (form). India. Ceylon. 

 Madagascar (var.). Azores (form). United States. 

 Brazil. Bolivia. Uruguay. Patagonia. 



C. Regnellii is nearly related to C. Meneghinii, but is easily 

 distinguished by its prominent lateral angles and broad, 

 straight apices. The lower parts of the sides of the semicells 

 are outwardly divergent in C. Regnellii, whereas the basal 

 angles of C. Menegliinii are rectangular. 



A small form was abundant from Hawkshead, Lancashire,, 

 in which the semicells were more regularly hexagonal and 



CJ t/ C_J 



the sinus was not so completely closed: length ll-12ju; 

 breadth 11-14 /.t ; breadth of isthmus 3 '5-4 /n ; thickness 6^ 

 (vide West, ' Alg. Engl. Lake Distr.' 1892, p. 725, t. 9, f. 20). 

 Certain forms were observed from Twenty-foot River, be- 

 tween March and Guyhirne, Cambs., which approached C. 

 Regnellii var. madagascariense W. & G-. S. West (' Alg. 

 Madag/ 1895, p. 58, t. (3, f. 39), but were proportionately 

 longer with a very narrow isthmus; length 16^; breadth 

 14*5 jit ; breadth of isthmus 3 /.<. 



109. Cosmarium Meneghinii Breb. 

 (PI. LXXII, figs. 29-32.) 



Cosmarimn Meneghinii Breb. in Ealfs' Brit. De?m. 1848, p. 9fi, t. 15, f. 

 [Cosmarium bioculatum 3L m^-h. 1837] ; Eal)enh. Flor. Enrop. Aly. Ill, 

 1868, p. 163; ? Eeinsch, Ccntrib. Alg.'et Fung-. 1875, t. 16, f. 5; Boldt, 



